1. Field of the Invention
This invention relates to a photoelectric conversion module (herein the term “photoelectric conversion module” used to mean both an optical to electrical conversion module and an electrical to optical conversion module), and more particularly, to a photoelectric conversion module with two circuit boards.
2. Description of the Related Art
In a network system such as a data center or the like, optical fibers as well as metal wires are used as a transmission medium for connection between servers, or between a server and a relay device such as a switching hub or the like.
The use of the optical fibers requires photoelectric conversion modules to convert electrical signals to optical signals, or optical signals to electrical signals. The photoelectric conversion modules are attached to be fixed to the relay device, or to be insertable to or removable from the relay device. The photoelectric conversion modules, which are attached to be insertable to or removable from the relay device, are called SFP (small form-factor pluggable) modules. Also, the photoelectric conversion modules are attached to be fixed to ends of the optical fibers, or to be attachable to or detachable from ends of the optical fibers.
In the case of the SFP modules, a photoelectric conversion module housing has an opening at one end in the insertion or removal direction, and in the opening of the housing, an end of a circuit board is positioned. The end of the circuit board is insertable into a slot provided in the relay device. The circuit board is inserted into the slot, thereby electrically connecting its photoelectric conversion module to the relay device.
Also, the photoelectric conversion module has in the housing photoelectric conversion elements, i.e. light emitting elements and light receiving elements, and the photoelectric conversion elements are optically coupled to the ends of the optical fibers respectively, via a lens. The photoelectric conversion elements are connected to a driver circuit mounted on the circuit board, and the driver circuit is electrically connected to the relay device.
As this type of the photoelectric conversion module, US2010/0080518A1 discloses a photoelectric conversion module having two circuit boards arranged to be parallel to each other.
The distance between the circuit boards is defined in accordance with the MSA (Multi-Source Agreement) between photoelectric conversion module venders. Accordingly, the distance between the circuit boards is held at the defined value, by a spacer being arranged between the two circuit boards.
Refer to US2010/0080518A1, for example.